The Finnish Sand Battery Is Brilliant.
By
Kiana Kazemi
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In the small Finnish town of Pornainen, a groundbreaking thermal battery is turning crushed soapstone—basically fireplace scrap—into a climate solution. Using excess renewable electricity, the system stores 1,000 megawatt-hours of heat in an insulated silo filled with sand. That’s enough to warm the town for an entire week during Finland’s frigid winters. It’s simple, low-cost, and it’s already helping the town slash its oil use and emissions.
The technology, built by Polar Night Energy, highlights a core principle that’s reshaping energy systems: store energy when it’s cheap and clean, and use it when it’s needed most.
At Harvest, we love this idea. We just bring it a little closer to home—literally.
We’re embracing similar principles with our thermal storage system, but with a focus on homes, not towns. Instead of sand, we use water, and instead of a district heating network, we provide smart, on-demand heating with air-to-water heat pumps. Our system stores energy when it's cheapest and cleanest, delivering savings, comfort, and a cleaner grid.
Our smart air-to-water heat pump charges when renewable electricity is abundant—like on sunny afternoons or windy nights—and stores that energy as heat in a thermal tank. Then, when energy is expensive or the grid is under strain, it shifts your heating load off-peak, keeping your home comfortable and your energy bills low.
The Finnish sand battery shows what’s possible at the community level. Harvest makes it personal—helping individual homeowners cut emissions, save money, and support a cleaner, more flexible grid without sacrificing comfort.
From the Finnish countryside to your utility closet, thermal storage is having a moment. And at Harvest, we’re making it easier than ever to be part of it.
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